Abstract : This paper presents the formal modelling of a nose gear velocity system, a
software-based system for estimating the ground velocity of an
aircraft. We employ the Event-B modelling language to conduct this
case study. Event-B allows us to construct and verify the formal
model of the system using the incremental refinement-based process.
The main goal of the case study is to highlight the need for
separating and integrating explicit semantics of application domain
into the formal development process. Traditionally in Event-B development,
domain descriptions of systems containing domain knowledge are
treated as second-class citizens, and the modelling is implicit and
usually distributed between the requirements model and the system
model. In this paper, we highlight the need for explicit modelling
of domain contexts as first-class citizens, and we illustrate
concepts related to implicit and explicit semantics with the help of an example
in Event-B.